Modifying the ExtensionNamespaceManager to disable only Java-based extensions

I'm looking to modify the ExtensionNamespaceManager to optionally
enable/disable its ability to execute Java class or package extensions
while leaving JavaScript extensions using the BSF intact. I started
off trying to overload the constructor to take a boolean, but realized
that I would be changing a lot of code to propagate the boolean down
to the places where this object is instantiated. Is the best way to
pass messages to this thing going to be to use a System property? Is
there any way to easily get access to the TransformerParameters?
The ExtensionNamespaceManager is only instantiated in the
org.apache.xalan.templates.StylesheetRoot class.

Thanks,
Bradley